We have applied a state-of-the-art environmental sustainability assessment to an energy positive sewage treatment plant, its supply chain and resource recovery processes. Resource recovery occurred through digestion of sewage sludge resulting in digestate and burning of the produced biogas with electricity generation. The digestate was after composting applied to land as a fertilizer. Important aspects of our study are: measurement of greenhouse gas emissions (including N2O), a holistic environmental impact assessment, and accounting for infrastructure, replacement of conventional fertilizers and toxicity of metals present in the digestate. Additional co-susbstrate is added to the digester. The impact of replaced products (conventional electricity and agricultural fertilizers) and direct sewage disposal was substracted from the environmental impact as such to obtain the net environmental benefit. Resource consumption was quantified as the cumulative exergy extracted from the natural environment (CEENE), addressing all relevant resource categories. Biodiversity loss and human health impact were calculated via the ReCiPe method. The complete system is estimated to have led to a prevention of resource extraction from nature (-2.5 MJex m-3 treated wastewater: 2.5 MJex saved). A negative global warming potential of -0.002 kg CO2-equivalents m-3 was obtained; the high impact of N2O emission was counteracted by displacement of greenhouse emissions of conventional electricity production and fertilizer production and application. On the other hand, mainly due to heavy metal toxicity induced by Zn present in the digestate, a damaging impact on human health was estimated up to a loss of 5.20 healthy seconds of human life m-3 treated wastewater. Hence, overall, it would be better, out of caution, to ﬁrst ﬁnd means to lower the heavy metal, especially Zn, content in the stabilized digestate before applying it to the land. A potential prevention of ecosystem damage (as biodiversity loss) was quantified, though for some impact categories this could not be quantified. One of the latter categories is marine eutrophication and the environmental benefit of nitrogen removal (one of the main aims of such a treatment plant) could hence not be expressed. Generally, the field of LCA needs further development to present a better and aggregated outcome.

@inproceedings{6883612,
abstract = {We have applied a state-of-the-art environmental sustainability assessment to an energy positive sewage treatment plant, its supply chain and resource recovery processes. Resource recovery occurred through digestion of sewage sludge resulting in digestate and burning of the produced biogas with electricity generation. The digestate was after composting applied to land as a fertilizer. Important aspects of our study are: measurement of greenhouse gas emissions (including N2O), a holistic environmental impact assessment, and accounting for infrastructure, replacement of conventional fertilizers and toxicity of metals present in the digestate. Additional co-susbstrate is added to the digester. The impact of replaced products (conventional electricity and agricultural fertilizers) and direct sewage disposal was substracted from the environmental impact as such to obtain the net environmental benefit. Resource consumption was quantified as the cumulative exergy extracted from the natural environment (CEENE), addressing all relevant resource categories. Biodiversity loss and human health impact were calculated via the ReCiPe method. The complete system is estimated to have led to a prevention of resource extraction from nature (-2.5 MJex m-3 treated wastewater: 2.5 MJex saved). A negative global warming potential of -0.002 kg CO2-equivalents m-3 was obtained; the high impact of N2O emission was counteracted by displacement of greenhouse emissions of conventional electricity production and fertilizer production and application. On the other hand, mainly due to heavy metal toxicity induced by Zn present in the digestate, a damaging impact on human health was estimated up to a loss of 5.20 healthy seconds of human life m-3 treated wastewater. Hence, overall, it would be better, out of caution, to \unmatched{fb01}rst \unmatched{fb01}nd means to lower the heavy metal, especially Zn, content in the stabilized digestate before applying it to the land. A potential prevention of ecosystem damage (as biodiversity loss) was quantified, though for some impact categories this could not be quantified. One of the latter categories is marine eutrophication and the environmental benefit of nitrogen removal (one of the main aims of such a treatment plant) could hence not be expressed. Generally, the field of LCA needs further development to present a better and aggregated outcome.},
author = {Schaubroeck, Thomas and De Clippeleir, Hayd{\'e}e and Weissenbacher, Norbert and Dewulf, Jo and Boeckx, Pascal and Vlaeminck, Siegfried and Wett, Bernhard},
booktitle = {Exergy, Life Cycle Assessment and Sustainability, 4th International workshop and symposium, Abstracts},
keyword = {exergy,OLAND,sustainability,wastewater treatment,life cycle assessment},
language = {eng},
location = {Nisyros Island, Greece},
title = {The net environmental benefit of a sewage treatment plant towards human health, natural ecosystems and resource/exergy consumption},
year = {2015},
}